Global warming is causing the Antarctic ice sheets to melt faster than previously thought, especially in West Antarctica.
An international research team led by the Alfred Wegener Institute has discovered that the root of this problem might lie in how the ice sheets originally formed.
Sediment samples from drill cores, combined with advanced climate and ice-sheet modeling, reveal that the permanent glaciation of Antarctica began around 34 million years ago.
However, this initial glaciation only covered East Antarctica. It took another 7 million years for ice to start advancing towards West Antarctica.
These findings were published in the journal Science.
About 34 million years ago, Earth underwent a major climate shift from a warm, greenhouse world with little ice to a cooler, icehouse world with large, permanent ice sheets.
This period saw the buildup of the Antarctic ice sheet. Until now, the specifics of how, when, and where this ice formed were unclear due to a lack of reliable data, particularly from West Antarctica.
Researchers from the Alfred Wegener Institute, along with colleagues from various international institutions, have now filled this knowledge gap.
They retrieved a drill core from the seabed off the coast of West Antarctica, near the Pine Island and Thwaites glaciers. This core provided crucial data on the early history of Antarctica’s ice.
Surprisingly, the core showed no signs of ice in West Antarctica during the first major phase of Antarctic glaciation.
“This means that the initial large-scale glaciation began in East Antarctica,” explained Dr. Johann Klages, the lead geologist. At that time, West Antarctica was still covered by dense forests and had a cool-temperate climate, preventing ice formation.
To understand the origins of the first permanent ice in Antarctica, researchers combined new data from the drill core with existing information on air and water temperatures and ice presence.
“The simulation supported our findings from the core,” said Prof. Dr. Gerrit Lohmann, a paleoclimate modeler. “This changes our understanding of the first Antarctic glaciation.”
According to the study, the right conditions for permanent ice formation existed only in the coastal regions of East Antarctica’s Northern Victoria Land.
Here, moist air masses met the high Transantarctic Mountains, creating ideal conditions for snow and ice. From there, the ice spread rapidly across East Antarctica but took another 7 million years to reach West Antarctica, which was mostly below sea level at the time.
“Our results show how cold it had to get before ice could advance to cover West Antarctica,” explained Hanna Knahl, a paleoclimate modeler. The study also highlights how East and West Antarctica react differently to climate changes. “Even slight warming can cause West Antarctica’s ice to melt again, which is happening now,” Klages added.
These findings are crucial for understanding the dramatic climate transition from a greenhouse to an icehouse world. They also improve climate models, allowing for more accurate simulations of how ice-covered areas impact global climate dynamics, including interactions among ice, oceans, and the atmosphere.
This research was made possible by a unique drill core retrieved during the 2017 PS104 expedition on the research vessel Polarstern. The MARUM-MeBo70 drill rig, developed in Bremen, allowed researchers to drill 10 meters into the seabed and collect samples from the hard seabed off West Antarctica, a task previously deemed impossible with conventional methods.
In summary, this study provides new insights into the history and dynamics of Antarctic ice sheets, shedding light on how they formed and how they might respond to future climate changes.
Source: KSR.
